Heater design for carbon allotrope ice protection systems

ABSTRACT

An ice protection system for an aircraft component includes a plurality of heaters. The aircraft component has at least two section and a junction area. At least one of the heaters is an H-shape carbon allotrope heater designed to apply heat to the junction area and prevent ice accumulation in the junction area.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application No.62/748,975 filed Oct. 22, 2018 for “HEATER DESIGN FOR CARBON ALLOTROPEICE PROTECTION SYSTEMS” by C. Slane, J. Hu, N. Ching, G. C. Botura, J.A. Mullen, M. J. Didyk.

BACKGROUND

This application relates generally to ice protection and specifically toice protection heaters.

An aircraft moving through the air is often subjected to ice formation,and anti-icing or de-icing devices must be used to remove or prevent icefrom accumulating on exterior surfaces of the aircraft. For any type ofelectrical heaters or de-icing heaters, the closer the heater is to theexternal surface of an airfoil, nacelle, nosecone, engine cowl, or otheraircraft part, the less power it takes to heat or de-ice the aircraftelement due to the proximity of the heater to the external surface.

In aircraft, electrothermal ice protection systems (IPS) containing suchheaters are applied to the backsides or embedded in leading edges toprovide the required heat to leading edge surface that are otherwisesubject to ice formation. Due to high thermal cooling loads on leadingedges while the aircraft is in flight, heat does not easily spread fromthe IPS along the leading edge to areas that do not have heatersdirectly underneath. For this reason, aircraft parts that containmultiple sections, segments or slates requiring breaking in the leadingedge surface are susceptible to ice growth in the joint or junctionareas not covered by IPS heaters edges.

SUMMARY

In one embodiment, an ice protection system includes a first section, asecond section attached to the first section by a joint, and a junctionsection, a first plurality of heaters expanding spanwise across thefirst section, a second plurality of heaters expanding spanwise acrossthe second section, a first H-shaped heater on the first section,expanding into the junction section, and a second H-shaped heater on thesecond section, expanding into the junction section. The first sectionhas a first span and a first chord. The second section has a second spanand a second chord. The junction section includes a portion of the firstsection and a portion of the second section proximal the portion of thefirst section

In a second embodiment, an ice protection system includes a componenthaving a plurality of sections and a plurality of heaters each having atleast one chordwise section connected to a spanwise section. Each of theplurality of sections is connected to the adjacent section by a junctionsection. One of the plurality of heaters resides on each of theplurality of sections, and each of the chordwise sections resides in ajunction section.

In a third embodiment, an H-shaped heater includes a first chordwisesection, a second chordwise section parallel to the first chordwisesection, wherein the first chordwise section and the second chordwisesection are aligned, and a spanwise section extending from a centralregion of the first chordwise section to a central region of the secondchordwise section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a heated leading edge with an iceprotection system (IPS) in a prior art configuration.

FIG. 2 is a schematic drawing of a heated leading edge with an IPSincluding an H-shaped carbon allotrope heater.

FIG. 3A-3B are schematic drawings of a heated leading edge with an IPSincluding an H-shaped carbon allotrope heater in a first embodiment.

FIGS. 4A-4B are schematic drawings of a heated leading edge with an IPSincluding an H-shaped carbon allotrope heater in a second embodiment.

DETAILED DESCRIPTION

A heater having at least one chordwise section connected to a spanwisesection can be used on aircraft components on or near junction sectionsto allow full heated coverage and ice protection. Such heatrs can beH-shaped, T-shaped, or L-shaped. For instance, an H-shaped heater hastwo chordwise sections connected at their center by a spanwise section.Similarly, a T-shaped or L-shaped heater has one chordwise sectionconnected to a spanwise section. This configuration can mitigate coldwhere component sections are joined to form a junction by allowingelectrical connection to chordwise sections that fit in such junctionsections. This approach can particularly be used with carbon allotropeslike carbon nanotube (CNT) based heater systems, as carbon allotropesystems allows for electrical connections at the end of each section ofa heater.

FIG. 1 is a schematic drawing of a heated leading edge 10 with iceprotection system (IPS) 11 in a prior art configuration. IPS 11 includesfirst section 12, second section 14, junction section 16, heaters 18with electrical connections 20, and cold section 22.

First section 12 and second section 14 of the leading edge can be, forexample, panels on a wing that are joined at junction section 16.Heaters 18 are on or embedded in each of first section 12 and secondsection 14 for ice protection. Heaters 18 can be, for example, carbonallotrope based heaters, metallic heaters, or other ice protectionsystems. Heaters 18 run spanwise S across each of component sections 12,14, and heat a large portion of sections 12, 14. Heaters 18 areelectrically connected to a power sources at electrical connections 20.

However, heaters 18 are unable to run across junction section 16, asfirst section 12 and second section 14 are manufactured as separate,removable assemblies; for example, they may be required to be installedor removed independently or move independently from one another duringflight as in the case of retractable slats. Because of this, duringflight, where there are high thermal cooling loads on IPS 10, heaters 18are unable to spread heat beyond the immediate area in which theyreside. This results in cold section 22 near junction section 16.Additionally, electrical connections 20 are the end of heaters 18 aregenerally cooler than the body of heaters 18. For this reason, theelectrical connections 20 on heaters 18 further contribute the creationof cold section 22. Cold section 22 is subject to ice formation becauseit is unheated. Ice formation in cold section 22 effects aerodynamics,wing operation such as power slats, and acts as an anchor for furtherice accumulation.

FIG. 2 is a schematic drawing of heated leading edge assembly 30 withIPS 31 including an H-shaped carbon allotrope heater. Leading edgeassembly 30 includes first section 32 with end portion 33, secondsection 34 with end portion 35, junction section 36 with joint 37,linear heaters 38, and H-shaped heaters 40.

Leading edge assembly 30 can be, for example, the leading edge on awing. A leading edge is one example of a component to which IPS 31 couldbe applied. For example, IPS could be applied to a leading edge of avertical stabilizer or horizontal stabilizer, or other componentscontaining a junction and needing even heating for ice protection.

Leading edge assembly 30 contains first section 32, second section 34joined at junction section 36. End portion 33 of first section 32 andend portion 35 of second section 34 are adjacent to each other and makeup junction section 36. Junction section 36 contains joint 37 wherefirst section 32 and second section 34 meet. Linear heaters 38 reside onand heat first section 32 and second section 34, but do not heatportions 33, 35, which make up junction section 36 surrounding joint 37.Instead, H-shaped heaters fill in space in junction section 36 and heatadjacent to joint 37 joining first section 32 portion 33 and secondsection 34 portion 35. In some embodiments, joint 37 can be a segment orintersection or one or more components or parts.

H-shaped heaters 40 promote ice protection and heating across componentsections 32, 34 including junction section 36. H-shaped heaters 40 havean electrical resistivity between between 0.005 ohms per square (Ω/sq)and 3.0 Ω/sq.

Each H-shaped heater 40 has two chordwise sections with length L₁ andwidth W₂, centrally connected by a spanwise (S) section with width W₁(about double the width W₂ of chordwise sections). The chordwise (C)sections are disposed on or embedded in first section 32 and secondsection 34 such that they extend out into junction section 36 past theends of linear heaters 38. This allows for chordwise sections to be asclose as possible to a joint in junction section 36 and eliminate thecold section 22 discussed in reference to FIG. 1.

The chordwise sections of the H-shaped heaters 40 are electricallycoupled to the spanwise sections and operated in anti-icing mode toprevent ice formation and growth. Various electrical configurations andspecific geometries can be used to provide different heating profilesdepending on the heating needs for the component to which H-shapedheaters 40 are applied. Physical and electrical layouts of heaters 40are discuss in more depth with regards to FIGS. 3A-3B and 4A-4B.

H-shaped heaters 40 are made of a carbon allotrope material. Forexample, carbon nanotubes (CNTs) are allotropes of carbon having agenerally cylindrical nanostructure, and have a variety of uses innanotechnology, electronics, optics and other materials sciences. CNTsare both thermally and electrically conductive, in addition to beinglightweight. Due to these properties, CNTs can be used as heaters toprevent icing on aircraft or other vehicles. Other carbon allotropes,such as graphene or graphene nanoribbons (GNRs), can also be used forheating or de-icing. Graphene has a two-dimensional honeycomb latticestructure, and is much stronger than steel, but is still electricallyand thermally conductive. GNRs are strips of graphene with ultra-thinwidths, typically less than 50 nm per strip.

Carbon allotrope heaters are uniquely beneficial for de-icing because oftheir high efficiency, light weight and ability to be molded intospecific shapes, and durability. They are more durable long termcompared to traditional metallic heaters, and can be shaped more easilyfor specific application needs.

FIG. 3A-3B are schematic drawings of a heated leading edge with an IPSincluding an H-shaped carbon allotrope heater in a first embodiment.FIG. 3A shows a physical layout of an IPS with H-shaped carbon allotropeheater, while FIG. 3B shows an electrical layout.

FIG. 3A is a schematic drawing of heated leading edge assembly 50 withIPS 51, main section 52, junction sections 56, linear heaters 58, andH-shaped heater 60. H-shaped carbon allotrope heaters 60 for use in IPSsystem 51 each include spanwise section 62, chordwise sections 64,positive electrical connections 66, and negative electrical connections68.

Sections 52, 56, and linear heaters 58 are similar to those componentsdiscussed in relation to FIG. 2. Main section 52 has both a span and achord. Linear heaters 58 are applied on main section 52 in a spanwisedirection. Linear heaters 58 do not reach junction sections 56.

The use of an “H” pattern design for heater 60 encompasses two chordwisesections 64 and one spanwise section 62. Chordwise sections 64 run alongthe chord of main section 52, while spanwise section 62 runs along thespan of main section 52. Chordwise sections 64 have equal lengths andrun parallel to each other. Spanwise section 62 connects chordwisesections 64 at the center of chordwise sections 64, forming an “H”shape.

Chordwise sections 64 lay close to the edges of the joints in junctionsection 56. This mitigates cold in junction sections 56 of leading edgeassembly 50. Chordwise sections 64 are electrically coupled withspanwise section 62 and can be operated in anti-icing mode to preventice growth.

In the embodiment of FIGS. 3A-3B, chordwise sections 64 host electricalconnections to heater 60. Positive electrical connections 66 reside onopposite ends of the first chordwise section, while negative electricalconnections 68 reside on opposite ends of the second chordwise section.Electrical connections to 66, 68, can be made through bus bar, wires,solder paste, or other appropriate connecting material that couplesheater 60 to a power source.

FIG. 3B is a schematic drawing of the electrical configuration ofH-shaped heater 60 on leading edge assembly 50. Here, linear heaters 58are shown with resistors 59. H-shaped heater 60 is shown with spanwiseresistor 70, and chordwise resistors 72, 74, 76, and 78.

Resistors 59 are each situated spanwise, centrally on one of linearheaters 58. Each of resistors 59 are equal to each other. Resistor 70resides on spanwise section 62 of heater 60. Resistor 70 is equal totwice of one resistor 59. Resistors 72, 74, 76, 78 reside on chordwisesections 64 of heater 60. Each of resistors 72, 74, 76, 78, is equal toone resistor 59.

This resistor configuration allows for consistent power throughoutheater 60 and the entire IPS on leading edge assembly 50. In someembodiments, this is accomplished by constant current and constantresistance. Alternatively, this is accomplished by variable current andvariable resistant to yield constant power.

FIGS. 4A-4B are schematic drawings of a heated leading edge with an IPSincluding an H-shaped carbon allotrope heater in a second embodiment.FIG. 4A shows a physical layout of an IPS with H-shaped carbon allotropeheater, while FIG. 4B shows an electrical layout.

FIG. 4A is a schematic drawing of heated leading edge assembly 80 withIPS 81, main section 82, junction sections 86, linear heaters 88, andH-shaped heater 90. H-shaped carbon allotrope heater 90 for use in anIPS system is in a different electrical configuration than heater 60.Heater 90 includes spanwise section 92, chordwise sections 94, positiveelectrical connection 96, and negative electrical connection 98.

Sections 82, 86, and linear heaters 88 are similar to those componentsdiscussed in relation to FIG. 2. Main section 82 has both a span and achord. Linear heaters 88 are applied on main section 82 in a spanwisedirection. Linear heaters 88 do not reach junction sections 86.

The use of an “H” pattern design for heater 90 encompasses two chordwisesections 94 and one spanwise section 92. This mitigates cold in junctionsections 86 of leading edge assembly 80. Here, the “H′ pattern of heater90 is a snakelike pattern running from positive electrical connection 96to negative electrical connection 98 in the shape of an “H.” Thebenefits of this configuration are that electrical connections areminimized while ensuring the entire “H” heats simultaneously. Electricalconnections 96, 98, can be connected in a fashion similar to thosedescribed in reference to FIG. 3A.

FIG. 4B is a schematic drawing of the electrical configuration ofH-shaped heater 90 on leading edge assembly 80. Assembly 80 includeslinear heaters 88 with resistors 89, H-shaped heater 90 with spanwisesection 92, chordwise sections 94, connections 96, 98, and resistors100, 102, 104, 106, 108, 110, 112, and 114.

On linear heaters 88, resistors 89 are each situated spanwise, centrallyon one of linear heaters 88. Each of resistors 89 are equal to eachother. Resistors 100, 102, 104, 106, 108, and 110 reside on chordwisesections of heater 90. Resistors 100, 102, 106, and 108 are equal inlength. Likewise, resistors 104 and 110 are equal in length. Resistors112 and 114 reside on the spanwise portion pf heater 90. This electricalconfiguration allows for variable electrical power throughout heater 90and leading edge assembly 80. This can be accomplished through constantcurrent with variable resistance.

Alternatively, H-shaped heaters can be replaced with T-shaped orL-shaped heaters. These heater shapes have at least one chordwisesection capable of being applied closely to the edge of a componentsection so that a resulting junction section is heated by the chordwisesection. Each of these shapes of heaters should also have at least onespanwise section connected to the at least one chordwise section. Thespanwise section allows for electrical connection between the chordwisesection across the component surface.

The heater having at least one chordwise section allows for mitigationof ice build-up in junction or joint sections on aircraft components.Ice build-up can interfere with normal wing operations, such as powerslats, in addition to affecting aerodynamics. Ice build-up can also actas an anchor, and promote additional ice growth or “bridging” whenallowed to accumulate in junction areas. The use of such a heaterstreamlines ice protection through the use of a spanwise connectingsection between two chordwise sections. Due to this geometry, additionalelectrical connections or circuitry are not needed to heat junctionsections.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

An ice protection system includes a first section, a second sectionattached to the first section by a joint, and a junction section, afirst plurality of heaters expanding spanwise across the first section,a second plurality of heaters expanding spanwise across the secondsection, a first H-shaped heater on the first section, expanding intothe junction section, and a second H-shaped heater on the secondsection, expanding into the junction section. The first section has afirst span and a first chord. The second section has a second span and asecond chord. The junction section includes a portion of the firstsection and a portion of the second section proximal the portion of thefirst section

The system of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

The ice protection system is applied to a component selected from thegroup consisting of wing leading edges, vertical stabilizer leadingedges, horizontal stabilizer leading edges, pylons, vanes, propellers,blades, engine inlets and surfaces requiring adjacent heaters.

The first and second H-shaped heaters each comprise two chordwisesections connected by a spanwise section.

The first and second H-shaped heaters further comprises a resistor onthe spanwise section and two resistors on each of the chordwisesections.

The first and second H-shaped heaters comprises an electricalresistivity between between 0.005 ohms per square (Ω/sq) and 3.0 Ω/sq.

The first and second H-shaped heaters each comprise a material selectedfrom the group consisting of carbon nanotubes, graphene, graphenenanoribbons, and combinations thereof

Electrical power is constant throughout each of the first and secondH-shaped heaters.

The first and second H-shaped heaters further include two positiveelectrical connections each at the end of a first chordwise section, andtwo negative electrical connections each at the end of a secondchordwise section.

Electrical power is variable throughout each of the first and secondH-shaped heaters.

Each of the first and second H-shaped heaters includes a positiveelectrical connection at one end of a chordwise section and a negativeelectrical connection at the one end of the chordwise section.

An ice protection system includes a component having a plurality ofsections and a plurality of heaters each having at least one chordwisesection connected to a spanwise section. Each of the plurality ofsections is connected to the adjacent section by a junction section. Oneof the plurality of heaters resides on each of the plurality ofsections, and each of the chordwise sections resides in a junctionsection.

The system of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

The system includes a plurality of linear spanwise heaters on each ofthe plurality of sections, and wherein each of the plurality of linearspanwise heaters do not reach the junction section.

Each of the plurality of heaters is H-shaped, T-shaped, or L-shaped.

Each of the plurality of H-shaped heaters further comprises at least onepositive electrical connection and at least one negative electricalconnection.

An H-shaped heater includes a first chordwise section, a secondchordwise section parallel to the first chordwise section, wherein thefirst chordwise section and the second chordwise section are aligned,and a spanwise section extending from a central region of the firstchordwise section to a central region of the second chordwise section.

The heater of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

The heater comprises a material selected from the group consisting ofcarbon nanotubes, graphene, graphene nanoribbons, and combinationsthereof

The heater includes a first positive electrical connection on a firstend of the first chordwise section, a second positive electricalconnection on a second end of the first chordwise section, wherein thesecond end is opposite the first, a first negative electrical connectionon a first end of the second chordwise section, and a second negativeelectrical connection on a second end of the second chordwise section,wherein the second end is opposite the first.

The heater includes a first resistor centered on the spanwise section, asecond resistor on the first chordwise section centered between thefirst end of the first chordwise section and the spanwise section, athird resistor on the first chordwise section centered between thesecond end of the first chordwise section and the spanwise section, afourth resistor on the second chordwise section centered between thefirst end of the second chordwise section and the spanwise section, anda fifth resistor on the second chordwise section centered between thesecond end of the second chordwise section and the spanwise section

The heater includes a positive electrical connection on a first end ofthe first chordwise section and a negative electrical connection on thefirst end of the first chordwise section.

The spanwise section has a first width, and each of the chordwisesections have a second width being half the size of the first width.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

1. An ice protection system comprising: a first section having a firstspan and a first chord; a second section having a second span and asecond chord attached to the first section by a joint; and a junctionsection comprising: a portion of the first section; and a portion of thesecond section proximal the portion of the first section; a firstplurality of heaters expanding spanwise across the first section; asecond plurality of heaters expanding spanwise across the secondsection; a first H-shaped heater on the first section, expanding intothe junction section; and a second H-shaped heater on the secondsection, expanding into the junction section.
 2. The system of claim 1,wherein the ice protection system is applied to a component selectedfrom the group consisting of wing leading edges, vertical stabilizerleading edges, horizontal stabilizer leading edges, pylons, vanes,propellers, blades, engine inlets and surfaces requiring adjacentheaters.
 3. The system of claim 1, wherein the first and second H-shapedheaters each comprise two chordwise sections connected by a spanwisesection.
 4. The system of claim 3, wherein each of the first and secondH-shaped heaters further comprises a resistor on the spanwise sectionand two resistors on each of the chordwise sections.
 5. The system ofclaim 1, wherein each of the first and second H-shaped heaters comprisesan electrical resistivity between between 0.005 ohms per square (Ω/sq)and 3.0 Ω/sq.
 6. The system of claim 1, wherein the first and secondH-shaped heaters each comprise a material selected from the groupconsisting of carbon nanotubes, graphene, graphene nanoribbons, andcombinations thereof
 7. The system of claim 1, wherein electrical poweris constant throughout each of the first and second H-shaped heaters 8.The system of claim 7, wherein each of the first and second H-shapedheaters further comprises: two positive electrical connections each atthe end of a first chordwise section; and two negative electricalconnections each at the end of a second chordwise section.
 9. The systemof claim 1, wherein electrical power is variable throughout each of thefirst and second H-shaped heaters.
 10. The system of claim 9, whereineach of the first and second H-shaped heaters further comprises: apositive electrical connection at one end of a chordwise section; and anegative electrical connection at the one end of the chordwise section.11. An ice protection system comprising: a component having a pluralityof sections, wherein each of the plurality of sections is connected tothe adjacent section by a junction section; and a plurality of heaterseach having at least one chordwise section connected to a spanwisesection, wherein each of the plurality of heaters resides on one of theplurality of sections, and wherein each of the chordwise sectionsresides in a junction section.
 12. The system of claim 11, furthercomprising a plurality of linear spanwise heaters on each of theplurality of sections, and wherein each of the plurality of linearspanwise heaters do not reach the junction section.
 13. The system ofclaim 11, wherein each of the plurality of heaters is H-shaped,T-shaped, or L-shaped.
 14. The system of claim 11, wherein each of theplurality of H-shaped heaters further comprises at least one positiveelectrical connection and at least one negative electrical connection.15. An H-shaped heater comprising: a first chordwise section; a secondchordwise section parallel to the first chordwise section; and aspanwise section extending from a central region of the first chordwisesection to a central region of the second chordwise section.
 16. Theheater of claim 15, wherein the heater comprises a material selectedfrom the group consisting of carbon nanotubes, graphene, graphenenanoribbons, and combinations thereof
 17. The heater of claim 15,further comprising: a first positive electrical connection on a firstend of the first chordwise section; a second positive electricalconnection on a second end of the first chordwise section, wherein thesecond end is opposite the first; a first negative electrical connectionon a first end of the second chordwise section; and a second negativeelectrical connection on a second end of the second chordwise section,wherein the second end is opposite the first.
 18. The heater of claim17, further comprising: a first resistor centered on the spanwisesection; a second resistor on the first chordwise section centeredbetween the first end of the first chordwise section and the spanwisesection; a third resistor on the first chordwise section centeredbetween the second end of the first chordwise section and the spanwisesection; a fourth resistor on the second chordwise section centeredbetween the first end of the second chordwise section and the spanwisesection; and a fifth resistor on the second chordwise section centeredbetween the second end of the second chordwise section and the spanwisesection
 19. The heater of claim 15, further comprising: a positiveelectrical connection on a first end of the first chordwise section; anda negative electrical connection on the first end of the first chordwisesection.
 20. The heater of claim 15, wherein the spanwise section has afirst width, and each of the chordwise sections have a second widthbeing half the size of the first width.